Single facer machines for making corrugated paperboard webs are well-known to those skilled in the art. In a typical modern single facer machine, a web of medium passes between meshing corrugating rolls and thereafter is held in the flutes of one of the corrugating rolls by fingers. For example, see Finger 54 in U.S. Pat. No. 3,390,040.
It is known to use vacuum in connection with one of the corrugating rolls to eliminate the fingers. Generally, fingers are objectionable in that they result in non-adhered streaks in the laminated singleface web. U.S. Pat. No. 657,100 discloses air shields designated I, I' juxtaposed to corrugating rolls for drying the web. U.S. Pat. No. 1,981,388 discloses circumferential grooves in a corrugating roll for receiving a suction tube which has holes for causing the web to adhere to the corrugating roll. U.S. Pat. No. 2,068,155 discloses two suction tubes interconnected by a groove in the corrugating roll for causing the web to adhere to the corrugating roll. British Pat. No. 2,005,595 discloses a single housing in place of the two suction tubes in the last mentioned patent and grooves in the corrugating roll for causing the web to adhere to the corrugating roll.
In addition, U.S. Pat. No. 3,947,206 teaches the utilization of longitudinal conduits connected to an external manifold to introduce suction through radial holes to the corrugated medium. It is known from U.S. Pat. No. 4,177,102 to interconnect the radial holes by a peripheral groove.